Ascochyta Leaf Blight: What is it and How Can You Get Rid of it?
americanarbor September 14, 2022

What is Ascochyta leaf blight?

Ascochyta leaf blight is very common disease that affects Kentucky bluegrass. It is also problematic for tall fescue and perennial ryegrass, among others, but it seems to affect Kentucky bluegrass most often. It can develop overnight, leaving your lawn looking drought-stressed and dead. Although it may seem intimidating, Ascochyta leaf blight isn’t as detrimental as it looks. Symptoms may begin to appear throughout the spring and early summer, and it’s especially common when rainy spring conditions lead to hot, drought-like summers.

What causes it?

Ascochyta leaf blight is caused by Ascomycete fungi. Although its development isn’t completely understood, it thrives in wet conditions in the springtime. Most often, Ascochyta leaf blight develops when soil conditions have not been properly maintained, and moisture levels have fluctuated greatly between very wet and drought-like periods.

Once it’s present in your lawn, you can exacerbate the problem by mowing frequently, especially with dull blades. This causes wounds to develop in your grass, allowing the disease to spread.

What does it look like?

Oftentimes, Ascochyta leaf blight resembles drought stress, leaving large, uniform patches of straw-like grass. It may look like your lawn is dead, but there may be healthy green blades of grass interspersed throughout. Ascochyta leaf blight can develop very quickly, beginning at the tips of each blade, and moving downward. Luckily, the roots are not usually affected.

What types of grass does it impact?

Most often, Ascochyta leaf blight affects Kentucky bluegrass, but it’s been known to be present in other types of grass, including tall fescue and perennial ryegrass. Since Kentucky bluegrass is prevalent throughout Colorado, Ascochyta leaf blight has become quite a nuisance.

Can it kill your lawn?

Although it may look like your lawn is quickly dying, Ascochyta leaf blight does not cause any permanent damage. This fungus affects the leaves of the plant, and it typically leaves the roots unaffected. While it’s not harmful, leaf blight can make your lawn look awful, and it can quickly ruin all the hard work you put into landscaping. Luckily, there are things you can do to prevent and manage Ascochyta leaf blight, so your lawn will be lush and green again in no time.

How can you get rid of it?

The best way to manage Ascochyta leaf blight is by preventing its growth in the first place. To do this, water your lawn consistently and deeply. Aim for one to 12 – 20 minutes of deep watering per zone every other day to maintain steady moisture and keep leaf blight at bay. Avoid watering at night to prevent the spread of the disease. It’s also important to mow your lawn when the grass is dry. Avoid early mornings and evenings when dew is present since the water will spread the fungi throughout your lawn. Aim for your lawn to be around 3 to 3 ½ inches in length, and try to mow about 1/3 off the top each time.

If your lawn does show symptoms of blight, simply encourage it to grow quickly. Since there is no fungicide available for Ascochyta leaf blight, your best bet is to encourage healthy growth so the affected grass grows out. The best way to do this is by fertilizing frequently and aerating your lawn in the fall to keep it healthy. 

If you’d like to learn more about how to keep your lawn healthy, strong, and fungi-free, contact us. Our experts at American Arbor Care are happy to help.

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